The present invention relates to an apparatus and method for the diffusion of substances between two fluids separated by a semipermeable membrane. More particularly, the apparatus of the present invention is mainly intended for use as blood oxygenator for mixing oxygen or oxygen containing gas into the blood of a patient before returning the blood to the patient.
Prior art blood oxygenators, which utilize a semipermeable membrane, such as for example, as shown in U.S. Pat. Nos. 3,212,498 and 3,332,746, have conducted a first fluid consisting of air, oxygen or some other oxygen mixture along one surface of a semipermeable membrane while the second fluid, consisting of blood to be oxygenated, is passed along the other opposing surface of the membrane. In this manner, a portion of the oxygen in the first fluid is diffused through the membrane and mixed with the blood flowing on the other side thereof.
In these prior art blood oxygenators however, only microscopic bubbles of oxygen or the gas mixture which are of a size capable of passing through the microscopic pores of the membrane are mixed with the blood, whereas larger bubbles of oxygen or gas mixture are excluded from passing through the membrane. In other words, with these prior art arrangements, the only means for oxygenating the blood is the diffusion through the microscopic pores of the membrane.